Drug delivery is the administration of a pharmaceutical agent to achieve a therapeutic effect in patients receiving the pharmaceutical agent. Conventional drug delivery strategies often require repetitive drug administrations and this can lead to strong fluctuating drug levels that may pose undue physiological discomfort to the patient. Furthermore, certain drugs at high concentrations can sometimes trigger undesirable toxicity or immunological responses in the patient, which may sometimes be detrimental.
As such, proper drug administration requires a fine balance between time, dosage, mode of delivery and more importantly, should aid in improving patient compliance and clinical outcomes. These factors consequently lead to the emergence of biodegradable polymer-based drug delivery carriers or vehicles, due to their ability to degrade to harmless by-products while providing desirable drug release profiles. In fact, designing these polymer-based delivery carriers or vehicles has been one of the focal points in numerous drug delivery studies in recent years.
Drug release profiles are usually altered through the direct tailoring of the chemistry or structural composition of the polymeric matrix. Subsequently, the release of the drugs is achieved either by diffusion through the polymer matrix, gradual dissolution of the polymer, by catalytic action from enzymes in-vivo or a combination of these. A great deal of work had been done in engineering a variety of different particle types, encompassing various shapes, sizes, morphologies, and in evaluating how these can affect drug release kinetics.
While the conventional approach in the literature largely revolved around designing of polymeric platforms for the administration of a single drug formulation, basic economics and patient compliance are factors that would favor the realization of a single carrier that can host and release multiple drug entities. Ideally, such carriers should be able to simultaneously entrap and release multiple drugs in a controlled manner, which would eliminate the need for repeated administrations. However, attaining such a carrier platform presents a major challenge in the field of drug delivery due to certain physicochemical considerations.